Ad hoc networking is a technology that enables wireless devices to form a cooperative communication network. Currently, there are various known air interfaces that support ad hoc networking, such as, for example, 802.11 and Bluetooth. Other well known fixed wireless networks (e.g., cellular) communicate through a point-to-multipoint configuration and depend on wide area coverage to deliver service to the end user. However, this type of configuration is not always capable of providing an adequate signal to the entire coverage area due to physical obstructions such as buildings that impede the signal. FIG. 1 illustrates an application of ad hoc networking that utilizes a known air interface to extend coverage for cellular systems, thus forming a hybrid communications network using ad hoc networking and cellular networking.
Cellular handsets CH1-CH13 are dual mode handsets capable of interoperating between a known cellular air interface, such as Wideband Code Division Multiple Access, and a known ad hoc networking air interface, such as Bluetooth. Thus, these cellular capable handsets CH1-CH13 are capable of forming a local ad hoc network by utilizing the Bluetooth device contained within the cellular handset. As a Bluetooth device, the local ad hoc network is referred to as a piconet. A Bluetooth piconet consists of a master device and some number of slave devices. A Bluetooth piconet typically has up to 7 active slaves that share a channel with the master. In addition, many more slaves can remain synchronized with the master in a parked state, but do not share the same channel. These parked slaves have less frequent communication with the master than the active slaves have with the master. When the Bluetooth device within a cellular handset CH1-CH13 is the master of a piconet, then the cellular handset is a master cellular handset of the piconet. Likewise, when the Bluetooth device within a cellular handset CH1-CH13 is a slave, then the cellular handset is either an active slave cellular handset or a parked slave cellular handset depending on its state within the piconet.
Cellular handsets CH1-CH7 are shown within a coverage hole 12 of a cellular wide area network (“WAN”) 10 having a cell site 11. The coverage hole 12 impedes cellular handsets CH1-CH7 from receiving an adequate cellular signal from the cell site 11. Cellular handsets CH8-CH13 have adequate coverage with the cell site 11, and the cellular handsets CH1-CH 7 therefore attempt to utilize the Bluetooth air interface to establish and maintain a voice call and/or a data call with one of the cellular handsets CH8-CH13 that is designated as the master. Another application of ad hoc networking is to utilize a dual mode cellular/air interface capability of the master to extend the capacity of the remaining cellular handsets among the cellular handsets CH8-CH13.
The cellular handsets CH1-CH13 form an exemplary piconet 13 having a master, one or more active slave cellular handsets being served by the master, and one or more parked slave cellular handsets. One known method for forming the piconet 13 designates the first cellular handset among cellular handset CH8-CB13 within the piconet 13 as the master with the remaining cellular handsets being designated as active or parked based on an order of appearance with the piconet 13 and the limit of active slave cellular handsets that can be served by the master. A shortcoming of this known method is the piconet 13 experiences limited throughput gains due in part to the designation of the slave cellular handsets as active or parked without regard to the capabilities of each slave cellular handset. Furthermore, the active slave cellular handsets may not be an optimal set of active slave cellular handsets to achieve the best throughput of piconet 13. For example, one or more active slave ecllular handsets may have the capability of receiving data directly from cell site 11 at a minimum data rate of 144 kbit/sec while some of the parked slave cellular handsets may not have the capability of receiving data directly from cell site 11 at a minimum data rate of 144 kbit/sec. Another shortcoming of the known method is the active slave cellular handsets having a low data rare relative to other active slave cellular handsets do not get priority in communicating with the master, and the average throughput of the piconet 13 can be significantly reduced.
The present invention advances the art by providing a method for facilitating a selection of an optimal set of active slaves within a piconet.